Electromagnetic indicator.



R. A. FESSENDEN.

ELECTROMAGNETIC INDICATOR.

APPLICATION FILED MAR. 14, 1908.

Patented Feb. 15, 1916.

INVENTOR,

BY M a? A TTORNE Y.

UNITED STATES, 136mm OFFICE.

REGINALD A. FESSENDEN, 0F BRANT BOCK, MASSACHUSETTS, ASSIGNOB, BY MESNEA SSIGNMENTS, TO SAMUEL M. KINTNER, OF PITTSBURGH, PENNSYLVANIA, AND

HALSEY M. Barman, or BLoomEIELn, NEW JERSEY, nnonrvnns.

ELECTROMAGNETTC INDICATOR..

Specification of Letters Patent.

7 Patented Feb. 15, 1916.

Application filed March 14, 1908. Serial No. 421,220.

ing instruments, or means for detecting the character and changes incurrents, something after the fashion of galvanometers, and especiallyadapted f0r-use with alternating currents though of course it. isequally suitable for continuous currents and other electricmanifestations by which a field of forceis altered. Its primary Objectsare to provide ainore sensitive and reliable indicating instrument, toincrease the power of the controlling field and avoid the ill effects ofheat in the conductors, and otherwise improve such mechanisms, as wellas provide superior means for observing or recording the changes ofcurrent, etc. These objects and other advantages to hereinafter appearare attained by means such as illustrated in two forms in. the accompanying drawing, wherein- Figure 1 is a central vertical section of oneform of indicator; Fig. 2 is a side elevation'of the indicating part ofa modified form of instrument, and Figs. 3 and 4 are sections on theline (3,4) of Fig. 2, showing two positions of the indicating wires.

One of the chief difficulties in obtaining a sensitive indicatinginstrument of this general type, is that the magnetic field employed islimited because the exciting current is limited owing to the wiresbecoming heated when they carry heavy currents. I not only obviate this,but also obtain great magnetic concentration and otherwiseimprove thesensitiveness of such instruments by keeping the field conductors cool,which may be done in various Ways as by placing the entire apparatus ina chamber cooled as by liquid air or other refrigerant, or else bymaking the field conductors hollow and cooling them by containedrefrigerating fluid. Also I make the readings more delicate by utilizingthe double'efi'ect of two or more moving elements which approach andrecede from one another on the passage of currents to be indicated.Thus. in Fig. 1 I provide a loop of a hollow conductor 6,

through which is circulated liquid air or other refrigerant, which hasthe double ef feet of lowering the resistance to current and alsocarrying away the heat, whereby very heavy currents may be employed, asfor 1nstance, several hundred amperes. A part or all of this fieldconductor loop 6 is preferably inclosed in vessel 7 which is preferablyvacuous and thus removes opposition-to motion of the moving parts, aswell as preventing the disturbances of air currents. Also within thischamber 7, and in the field of the conductor loop 6, I provide a fineWire loop 11, 12, which? may be conveniently kept under regulabletension and is provided with thickened portions 13 in order to increasethe visibility or the width of the shadow of the Wires seen through thewindow 8, and to make them vibrate more definitely. The wire loopmay bebalanced and stretched by a pulley 14 attached to a spring 15 and to anarmature 16 which is drawn down against the effort of spring 15 by thecore 17 of a coil 18, whose strength is regulated by the battery-19 andadjustable resistance 20. Of course any other means for regulating thetension on the wires may be employed and this tension will adjust thenatural period of vibration of the indicating wires 11 and 12. It willfree to move, the instrument is very sen sitive and easily read. Ofcourse any desired means may be used for recording the motions of theindicating wires.

In the modification shown in Figs. 2,3, 4,

the apparatus is adapted to be placed in a chamber 'cooledby liquid airor other refrigerant in any convenient way; or it may be used bodily inplace of the wires 11 and 12 in the apparatus of Fig. 1,replacing theWires 13' therein. It comprises essentially a field of force such asproduced by the magnetiz ing coil 21, and a series of wires or a coil ofthe wire 22 stretched in the field so as to lie in two parallel planes,as indicated in Figs. 3 and 4. lt is preferable to so mount them on bars24 that normally the series of wires 23 alternate in position with theseries 23*, so that light coming in the direction of the arrow in Fig. 3is shut 0d by the wires. When a'current passes through the wires 23however, the cooperation with the magnetic fieldwill cause them to shiftposition so that they will stand in register and permit light to passthrough as indicated in Fig. 4. This efiect can be observed directly bythe eye or telescope, or obviously recording means copld be employedsuch as a traveling photo sensitivesurface 26 on rolls 27 exposed toaportion of the light let through a perforated screen 28. Obviously atension adjustingmeans, such as illustrated in Fig. 1 could also. beapplied to the wires in Fig. 2 or they may be adjusted by screws 25 soas to regulate their natural period of vibration. In ,this

device again, the indication is produced by the cumulative effect of themotion of the indicating wires, which makes the instrument verysensitive in addition to the advantage of using very strong currents forthe magnetic field. I

Having thus described my invention and illustrated its use, What llclaim as new and desire to secure by Letters Patent, is the following:

1. An electromagnetic indicator comprising a loop of indicating wirewhose members are adapted to be relatively laterally moved by changes ina field of force, and a loop of hollow cooled conducting wire arrangedto form a fieldof force, substantially as-described. p

2. A galvanometer comprising a conductor adapted to produce a field offorce, two

parallel sets of stretched wires suspended in' said field, and means forobserving their movements relative to each other.

3. A galvanometer comprising a conductor adapted to produce a field offorce, two parallel sets of stretched wires suspended in said field, andmeans for observing and recording their movements relative to eachother.

A. A galvanometer com-prising a conductor having parallel portionsadapted to pro duce a field of force, and plurality of wires stretchedin midfield of force and adapted to give an exaggerated indication by motions in opposite directions, substantially as described.

5. A galvanometer for high frequency.

suspended in said field and arranged to move laterally in oppositedirections, and means to observe variations in the amount of lightadmitted through the wires when they vibrate. 1

7. A galvanometer comprising a field pro ducer formed of a hollowconductor cooled by liquid therein, and an indicator-having several setsof parallel closely spaced wires mounted in said field, and means forobserving the motions of said wires relative to each other,substantially. as described.

In testimony whereof l have hereunto signed my name in the presence ofthe two subscribed witnesses.

REGINALD A. FESSENDEN.

Witnesses:

A. STEIN, J12, Jnssin E. BENT.

